THEpresent research represents an effort to standardize a colorimetric procedure for the rapid determination of small quantities and the detection of minute changes in the concentration of dissolved silica in natural waters of very low phosphate content.A preliminary study indicated that two general procedures were available. The method of Dienert and Wandenbulcke (4) takes advantage of the yellow silicomolybdate color produced when ammonium molybdate reacts in acid medium with dissolved silica. Isaacs' method (7) attempts to extend the sensitivity of this reaction by reducing the molybdenum in the silicomolybdate complex to the relatively intense molybdenum blue color.

No abstract